1. Field of the Invention
This invention relates to a device for detecting a particular color in color negatives or originals, and more particularly to a device for determining whether or not a particular color especially desired to be reproduced in a good condition such as flesh color is included in color negatives or originals.
2. Description of the Prior Art
It is generally desirable to be able to obtain color prints of proper color balance and density even from color negatives or originals having undesirable color balance and density. At the same time, since, depending on the subject matter of the photograph, most observers are concerned about a particular color as flesh color, green of green grass or blue of sky or water, it is often desirable that one of these colors be reproduced in particularly good condition. In other words, color prints in which such particular colors are not reproduced in good condition are apt to be regarded as unsatisfactory prints. According to an investigation conducted by the inventors, about 80% of the time the principal subject matter of color negatives is the human figure. Therefore, it is especially desirable that flesh color be reproduced in a good condition.
As is well known in the art, color prints of high quality, i.e., color prints of proper color balance and density, can be obtained even from color negatives of undesirable color balance and density by controlling the exposure in a photographic color printer.
In determining exposure in color printers, various methods have been known and practically employed. A well-known printing system in which the printing light source intensity is adjusted during red, green and blue exposures to levels which will normalize the resulting integrated transmittances to a near-neutral color balance, i.e., "gray", is based on U.S. Pat. No. 2,571,697, Evans. This printing system produces satisfactory results from a large majority of the negatives of a given type of film. It has also been known in the art to adjust the rate of correction for red, green and blue exposures based on a linear combination of the red, green and blue large area transmission densities (LATD) of the original to be printed.
Since the above described conventional printing systems are based on integrated transmission measurements conducted over the whole area of the original, the obtained prints are not always satisfactory. For instance, if the background of the principal subject matter is primarily red (red curtain or furniture), green (green grass or foliage) or blue (blue sky or water), color correction based only on the aforesaid LATD system is unsatisfactory. This problem is known as "color failure".
Further, if the background of the principal subject matter is of particularly high or low brightness, the conventional correction based on the integrated transmission density does not give satisfactory results. For example, when the principal subject matter has been photographed with a back light or in a spotlight conventional correction will give unsatisfactory results. This is known as "density failure".
According to the inventors' tests, in the color printing process using the LATD printing system the yield of satisfactory prints is about 70% of all the prints obtained.
It has also been known in the prior art to determine the exposure in a color printer based on the measured densities of divided areas of color originals in which the entire area of the original is divided into upper and lower, right and left, and central and peripheral sections. The exposure is determined based on a combination of the LATD and the densities of the divided areas. In this system, the yield of satisfactory prints is somewhat raised. However, since the density of the principal subject matter is not accurately measured in this system, the correction is not always effected in the most desirable manner.
In order to solve the above described problems in a photographic color printing process, there has been proposed a novel method of color printing in which the color negatives are printed based on a predetermined particular color when the color negatives have a predetermined particular color as the principal subject matter and the color negatives or originals are printed according to the conventional LATD printing system or the like when their principal subject matter does not have the particular color (U.S. Patent Applications Ser. Nos. 808,903 and 817,059).
In this method, the red, green and blue densities of a color negative are measured at a number of points thereon. A point is determined to have the predetermined particular color when the measured values of red, green and blue densities fall within a predetermined region in a chromaticity coordinate system when plotted therein. Thus, the particular color is defined by a particular region in the chromaticity coordinate system, which may be a three-dimensional system or a two-dimensional system the axes of which represent the red, green and blue densities or combinations of the three color densities.
When the negative has more than a certain number of points of the particular color, it is determined that its principal subject matter has the particular color and that the negative is to be printed based on the particular color.
It has been found that the yield of satisfactory color prints can be substantially raised in accordance with this method. However, in this method there is a problem that errors in determination of the color of the individual points may occur in some types of color negatives when various types of color negatives having different gamma values and sensitivities are used, since the densities vary depending on the gamma value and sensitivity of the film even if the same subject matter is photographed under the same conditions.